9.25-16 tyres - What's the story?
 

Recently picked up a few NOS runflat 9.25-16 tyres. Is there anything out of the ordinary relating to the 9.25 sizing? The reason I asked is that when place alongside 9.00-16 tyres, the 9.25's appear smaller in width and diameter. Is the sizing something like trousers where a size 6 and 6 1/4 are completely different?

Here is a 9.25-16 Dunlop T26 alongside a 9.00-16 Simex ST24.
The tread patterns are slightly different so the T26 looks narrower to start with, but the actual width of the carcase and diameter is significantly smaller than the 9.00-16:

I thought that maybe the Simex tyres were perhaps just a "Built big" tyre, so I compared a few original WW2 9.00-16's.
Here is a NOS Firestone 9.25-16 up along a WW2 (worn) Firestone 9.00-16 sand style tyre. The 9.00-16 has lots of flat spots and is not inflated, but it seems to be a larger diameter and is definately wider (could it be the sand flotation design? If larger than 9 inches, why not call it a 9.50 or 10.00?)

Hi Tony,

The Simex tyre is out of the original Dunlop Trackgrip mould so is not extra large or built bigger. The 9.25-16 RF was fitted to Humber scout cars and with the non availability of 9.25 now, the Trackgrip RF 9.00 (Ferret tyres) are substituted. This makes bottom gear very high and also makes it difficult to fit a spare wheel to the vehicle. As to why the 9.25 is smaller than the 9.00, I have not been able to find anything on that.

Richard